1. Technical Field
The invention relates to a color converter, a color converting method, and a color conversion program, and more particularly, it relates to a color converter and a color converting method and a computer readable medium for storing a program for making a computer execute a process for color conversion for converting the color of a color image signal when the color reproducible region of the color image signal is different between an input side and an output side.
2. Related Art
As a device for outputting a color image, there are display devices such as a CRT and a color LCD and printing devices such as a printer. Among these output devices, the reproducible color range is different because of a difference in an output method. A CRT may reproduce a vivid color in a region with high brightness because its output method is a fluorescent material lighting type. On the other hand, It is difficult to for a printer to reproduce a color with high brightness and high saturation other than the primary color because it generates a color while overlaying the color materials, and on the whole, it may reproduce a color in a region with low brightness.
In this way, color reproducible region is various depending on the output device. Therefore, when the same image data is supplied by the different output device, for example, when an image created on a CRT is printed by a printer, there may exist a color which is not able to be reproduced. For example, a color with high brightness and high saturation may be outputted on a CRT, but sometimes it may not be reproduced by a printer. On the contrary, a color with low brightness and low saturation may be reproduced by a printer, but sometimes it may not be displayed on a CRT. Therefore, at least the non-reproducible color is converted into a color that looks closest to it and outputted to the output device, thereby reproducing the whole image in the best quality in the output device. At this time, color mapping for substituting a color within the color reproducible region of the output device for a given color image signal is required.
As a conventional color mapping technique, there is a technique in which color conversion coefficients corresponding to various purposes are prepared and a color is converted with a color conversion coefficient corresponding to a desired purpose. For example, there is a color conversion using an ICC profile. In the ICC profile, three intents (Perceptual, Saturation, Relative Colorimetric) are prepared. These three modes are widely different in the purpose of use; for photo, for graphics, and for calorimetric matching and they don't necessarily agree with a user's purpose.